The primary purpose of this project is to measure the retention of zinc when three dietary sources -- a zinc salt, zinc animal foods, and zinc plant foods -- are fed to pregnant and nonpregnant women. A liquid formula diet providing the Zn pregnancy RDA (20 mg/day) will be used for all the studies. Semipurified foods will be used for the diet providing zinc as a chemical salt, but natural foods will be used for the other two diets. The animal diet will provide 70% of the zinc form animal sources; the plant diet provides 70% from plant sources. Zinc absorption will be evaluated from balance studies, excretion of a stable isotope, and postprandial zinc uptake after a load dose. Preliminary studies show that pregnant women excrete significantly more zinc in their urine thant nonpregnant women even though their serum are lowered significantly. Therefore, differences in serum zinc binding in pregnancy and possible associated changes in renal filtration will be investigated. Ancillary studies include measurement of possible biochemical indicators of zinc status in pregnancy, i.e. serum, urinary, hair and saliva zinc levels and the activity of some zinc-dependent enzymes. Nitrogen, calcium, magnesium and copper retention will also be measured in the pregnant women on the three dietary regimens. Studies on energy expenditure, body composition and vitamin availability are planned as well.